A Sensor-Integrated "Smart" Ureteral Stent and Wireless In-Vitro Test for Real-Time Obstruction Detection

Every year, millions of stents are used globally to prevent ureteral obstruction for various causes. However, indwelling stents are susceptible to failure by encrustation that re-blocks urine flow, leading to kidney swelling known as hydronephrosis, and if unrecognized, resulting in kidney damage. Toward enabling early detection of obstruction in stented ureters, this paper reports an advanced double-J stent with an integrated microsensor and antenna circuitry, making smart ureteral stents capable of wireless kidney pressure monitoring a reality. This stent device acts as a radiofrequency resonator with a pressure-sensitive resonant frequency that is externally read and continuously tracked to detect changes in renal pressure in vivo. The prototype is microfabricated using a standard 8-Fr ureteral stent. Experimental testing of the device demonstrates wireless pressure sensing with 3.1-kHz/mmHg sensitivity in artificial urine, revealing an order-of-magnitude improvement over the preceding design, while covering a pressure range well sufficient to detect hydronephrosis.